Automatic tablet coating apparatus



Feb. 28, 1956 ETAL 2,736,288

AUTOMATIC TABLET COATING APPARATUS Filed May 2 1954 2 Sheets-Sheet 1 BLOWER l6 ll MOTOR 2 TANK IO 32 u f Fl 6. l.

39 34 TIMER MOTOR X STARTER MOTOR M L STARTER Fl 6. 3. |7 3s MOTOR STARTER INVENTORS EDWARD B. CLAY 8: BY ALFRED J'. D'ANGELO ATTORNEY Feb. 28, 1956 E. B. CLAY ETAL 2,736,288

AUTOMATIC TABLET COATING APPARATUS Filed May 2 1954 2 Sheets-Sheet 2 INVENTORS. EDWARD B. QLAY a He 2 BY ALFRED J. DANGELO ATTORNEYS United States Patent AUTOMATIC TABLET COATING APPARATUS Edward B. Clay, Philadelphia, and Alfred J. DAngelo, Penn Valley, Narberth, Pa., assignors to Smith, Kline & French Laboratories, Philadelphia, Pa., a corporation of Pennsylvania Application May 28, 1954, Serial No. 432,977

3 Claims. (Cl. 118-19) This invention relates to apparatus for coating small objects such as, for example, tablets or similar pharmaceutical preparations by application of a liquid having a coating material in solution or suspension.

Heretofore in the tablet coating art, the tablets were coated manually and the operator was required to maintain a proper time interval between the various coats, gauge the correct amount of coating syrup to be applied, apply the syrup in a correct and constant manner so that it adhered to the tablets and not to the surface of the coating pan, keep the syrup reservoir free from dust and other contaminates and to move a syrup container or reservoir from one coating pan to another.

It will be appreciated that this manual method of applying coatings is a time consuming and costly operation, requiring the constant attendance of an operator. Further, manual coating sometimes results in uneven application of the coating to the tablets which necessitates rejection of the batch.

It is, therefore, an object of this invention to provide an automatic tablet coating apparatus which times the interval between the coats.

It is a further object of this invention to provide an automatic tablet coating apparatus which delivers a predetermined quantity of syrup or coating liquid at the end of each time interval.

It is a further object of this invention to provide an automatic tablet coating apparatus which applies the syrup or coating in a uniform manner to the mass of tablets.

It is a further object of this invention to provide an automatic tablet coating apparatus in which the syrup or coating liquid is kept free from contamination in an easily cleaned and refilled container.

It is a further object of this invention to provide an automatic tablet coating apparatus which contains suflicient syrup or coating liquid so that it may be operated over an extended period of time, thus eliminating the need for frequent refilling of small containers and thus reducing the amount of manual labor required.

These and other objects of the invention will become apparent from the following description when read in conjunction with the accompanying drawings, in which:

Figure l is a diagrammatic representation of apparatus embodying the invention;

Figure 2 is an elevation showing a portion of the apparatus shown in Figure 1; and

Figure 3 is a diagram of the electrical circuit involved.

A rotary coating pan 4 rotates on two tires 6 which are supported on rollers mounted in housing 8 on the four corners of supporting framework 2. It will be appreciated that the rotary coating pan 4 may be made of steel, plastic or other similar desired material. The coating pan 4 is driven by a shaft 10 and a motor 11. The shaft 10 has a gear 12 mounted thereon which engages a ring gear 14 affixed to the circumference of the coating pan. The coating pan is also provided with open ends 16 for introducing and removing materials from the pan. On the left-hand side of the coating pan, as viewed in the draw- ICE ings, there is a stationary dust manifold 18 which is connected to a vacuum blower 15 by means of a conduit 21. The vacuum blower serves to draw a current of air through the pan 16 which serves to remove any dust caused by attrition of the tablets in the pans. Furthermore, the current of air through the pan serves to hasten the drying of the coating liquid.

The air duct 21 shown in Figure 1 is provided with 8. depending vane 23 suspended from a transversely extending rod 25 which passes through the walls of the duct. The vane is positioned internally of the duct in the path of air flow therethrough. An arm 27 is affixed to the rod 25 externally of the duct and is adapted to engage a limit switch 29 when the vane is in a downward position as shown in the drawing. The weight of the vane is such that, when no air is flowing through the duct 21, the limit switch 29 is closed by pressure of the arm 27 thereon, and when air is flowing through the duct 21, the vane is displaced offering substantially no resistance to air flow through the duct and the limit switch 29 is closed.

A portable container 21 for'coating liquid maybe positioned adjacent to the rotary coating pan 4 in any desired location. The portable container 20 is provided with a valve 22 mounted on a line leading from the bottom of the container. A flexible line 24 is connected to the valve 22 by means of a clamp 26. The flexible line 24 is joined to a pipe 28 which connects with valve 30 at its opposite end. Valve 30 is mounted on a nipple threaded into the suction side of pump 32.

Pump 32 is driven by electric motor 34, said motor being connected to the pump 32 by belt 36. Motor 34 has a conduit 38 connected thereto which is joined to timer 4%) at its opposite end. Timer 40 may be of any desired type such as a standard duplex timer. This timer has two scales thereon, scale 42 reading in seconds and scale 44 reading in minutes. A conventional on-ofif switch 46 is mounted on the timer housing.

Secured to the discharge side of the pump 32 is flexible line 48. Flexible line 48 is secured to a pipe 50 which passes through a hole in stationary dust manifold 18. Pipe St? is provided with an elbow 52 at its inner end so that liquids discharged therefrom are directed downward-1y. Pipe St? is slidably mounted in dust manifold 18 so that it may be withdrawn from the center of the coating pan when desired.

In Figure 3 there is shown three conventional motor starters 31, 33 and 35. These starters are connected to a suitable source of power through a conventional disconnect switch 37. The motor starter 31 controls operation of the pump motor 34. The motor starter 33 controls operation of the pan motor 11. Starter 35 controls operation of the blower motor 17.

The on-otf switch 46 of the timer 40 connects the timer to a suitable source of power through the switch contacts 29 and 39. The switch 29 is the limit switch in the blower duct and is closed only when a suflicient current of air is passing through the duct to insure the removal of dust and adequate drying of a coating syrup in the pan. The switch contact 39 is positioned to be closed upon energization of a solenoid coil 41. The solenoid coil 41 is connected by means of conductors 43 to the output side of the motor starter 33. Thus the pump motor 34 can be operated by means of the timer 40 and the motor starter 31 only when a suflicient air flow is passing through the air duct 21 to open the switch 29 and when the pan motor 11 is energized and the pan 4 is rotating.

The operation of the apparatus is as follows: A batch of uncoated tablets is placed in the rotary coating pan 4. The portable container 20 is then filled with the desired coating liquid which may be a sucrose solution for example. The elbow 52 is positioned in the center of a e3 coating pan in the position shown in the drawing and the coating pan is rotated by the pan motor 11-.

Thereafter, the blower motor 17 is started, the pan motor 11 is started and then the valves 22 and 30 in the line from the container 20 are opened and motor '34 is energized by a tripping switch 46. The amount of syrup or coat and the time interval between the coats is controlled 'b'y presetting timer 40 using scales 42 and 44. Thus the timer will energize the motor 34 for a predetermined period which will feed a certain quantity of syrup from the container 20 to the coating pan 4 and will also regulate the time interval between the application of successive coats. It is necessary that these two factors be closely controlled since, if an incorrect quantity of coating syrup is applied, it does not become evenly distributed upon the tablets and the time interval between the application of successive coats must be long enough to permit the coatings to dry. Once the proper times for these two operations have been determined, the automatic timer may be set for a repeating cycle and no attention by the operator is necessary. 'If for some reason the operation of the pan motor should be interrupted or the flow of air thioughthe duct 21 should be reduced below the flow rate required to -l eep open the switch 29, the flow of control power to the timer 40 will be interrupted by either the switch 29 or the switch 39 and operation of the syrup pump motor 34 will be arrested.

It will be obvious to those skilled in the art that many modifications of the present invention are possible without departing from the spirit thereof and the scope of the present invention is to be restricted only in accordance wi-th'the appended claims.

What is claimed is:

1. Apparatus for coating small objects 'comprising a rotatable coating pan, means for rotating said pan, a container for coating liquid, a pump having its intake side connected to said Container, an open discharge line connected to said pump and terminating in said coating pan, means for providing a flow of air through said pan, coin trol means responsive to the flow of air, and timer means responsive to said control means for actuating said pump at fixed intervals of time for a predetermined length of time.

2. Apparatus for coating small objects comprising a rotatable coating pan, means for rotating said pan, a container for coating liquid, a pump having its intake side connected to said container, an open discharge line connected to said pump and terminating in said coating pan, means providing a 'flow of air through said pan, timer means for actuating said pump at fixed intervals of time for a predetermined length at time, and means responsive to operation of said pan rotating means and to the How of air provided to said pan for controlling operation of said timer means.

3. Apparatus for coating small objects comprising a rotatable coating pan having two open ends extending transversely of the axis of rotation, means for roating said pan, 'a container for coating liquid, a pump having its intake side connected to said container, a discharge line connected to said pump and terminating in said coating pan, a motor for driving said pump, a stationary air duct having 'OI16 end positioned adjacent to one open end of said rotatable pan, means for providing a flow of air through said air duct and said pan, means in said air duct responsive to flow of air therethrough, timer means for actuating said pump motor at fixed intervals of time for a predetermined length of time, and means responsive to said air flow responsive means and responsive to operation of said pan rotating means for preventing operation of said timer means in the event of failure of air fiow or failure of pan rotating means operation.

References Cited in the file of this patent UNITED STATES PATENTS 393,616 Case Nov. 27, 1888 2,477,269 Sandler July 26, 1949 2,671,009 Comstock Mar. 2, 1954 

1. APPARATUS FOR COATING SMALL OBJECTS COMPRISING A ROTATABLE COATING PAN, MEANS FOR ROTATING SAID PAN, A CONTAINER FOR COATING LIQUID, A PUMP HAVING ITS INTAKE SIDE CONNECTED TO SAID CONTAINER, AN OPEN DISCHARGE LINE CONNECTED TO SAID PUMP AND TERMINATING IN SAID COATING PAN, MEANS FOR PROVIDING A FLOW OF AIR THROUGH SAID PAN, CONTROL MEANS RESPONSIVE TO THE FLOW OF AIR, AND TIMER MEANS RESPONSIVE TO SAID CONTROL MEANS FOR ACTUATING AT FIXED INTERVALS OF TIME FOR A PREDETERMINED LENGTH OF TIME. 